1. Technical Field
The present invention relates to improvements in methods and apparatus for brushing teeth and, more particularly, to toothbrushes having bristles that are rotatable relative to the brush head in response to linear reciprocation of the brush handle.
2. Discussion of the Prior Art
It has long been recognized to be advantageous to apply a rotary brushing action to teeth for the purpose of removing deposits that build up on tooth surfaces, particularly adjacent the gumline. The desired brush rotation is about an axis perpendicular to the tooth surface and, for the usual toothbrush configuration, is approximately perpendicular to the brush handle. The hand manipulation required of a conventional toothbrush to effect this desirable rotary brushing action is difficult at best, particularly in view of the small surface area to be cleaned and the small radius of movements of the hand required to accomplish the necessary brush strokes. Powered toothbrushes have been employed to accomplish the desirable rotary brush action but have achieved only, limited commercial success, primarily because of the reluctance by many consumers to place a powered implement in their mouths. Examples of such powered toothbrushes for effecting rotary brush action of the type describe are found in U.S. Pat. Nos. 1,265,536 (Sharps), 1,947,324 (Zerbee), 4,156,620 (Clemens), 4,274,173 (Cohen), 4,827,550 (Graham et al) and 4,845,795 (Crawford et al).
In point of fact, consumers are most comfortable with nonpowered toothbrushes requiring longitudinal reciprocation of the handle to effect brushing. The present invention is concerned with providing an efficient and inexpensive non-powered (i.e., operated solely in response to movement of the user's hand) technique for converting longitudinal brush handle reciprocation to the desired rotational brush strokes. There have been a number of commercially unsuccessful attempts to accomplish this desirable result. For example, in U.S. Pat. No. 1,557,244 (Domingue) there is disclosed a plurality of brush elements, each including plural tufts, mounted in a brush head by means of toothed pinions that are caused to rotate by longitudinal reciprocation of a rack secured to the brush handle and extending into the brush head. However, in order to use this brush, the brush head must be held stationary with one hand while the handle is reciprocated with the other hand. Such two-handed operation has not achieved acceptance among consumers, most likely because of the difficulty involved in holding the brush head stationary while cleaning teeth located in the back and sides of the mouth.
Although the apparatus disclosed in the aforementioned U.S. Pat. No. 4,156,620 (Clemens) is a powered toothbrush, it is of background interest for the present invention because of its disclosure of a power driven rack that is longitudinally reciprocable to cyclically rotate a plurality of single tuft brush elements. Each tuft is controllably rotated about its central axis at a speed of approximately three thousand revolutions per minute. Since each brush element is a single tuft rotated about the central tuft axis, the individual bristles are caused to alternately twist in helical fashion and then release in a manner described by Clemens as essential in providing the desired tooth cleaning action. In addition, the single tuft elements of the Clemens device are rotated for equal numbers of revolutions in opposite directions during each cycle. The high speed, multiple revolution, twisting operation results from the power driven nature of the device. As noted above, consumers are most comfortable with nonpowered toothbrushes.
In U.S. Pat. No. 1,620,330 (Douglass), there is a disclosure of plural brush sections symmetrically disposed about respective axes and mounted on the brush head to be freely rotatable about those axes relative to the head. However, there is no mechanism provided for positively rotating the brushes in response to longitudinal reciprocation of the brush handle. In fact, true longitudinal movement of the brush handle creates purely radial, as opposed to tangential, net forces on the rotatable brush sections so that there is no turning force applied thereto. Accordingly, in the absence of some mechanism for positively converting the longitudinal forces to rotational forces, there is negligible rotation of the symmetrically mounted brush sections.
In U.S. Pat. No. 1,212,001 (Baxter) there is disclosed a toothbrush having plural brush sections mounted eccentrically on the brush head for pivotability between stops about respective axes. Once again, there is no positive mechanism for rotating the brush sections; rather, the frictional engagement between the ends of the bristles and the surfaces of the teeth provides the force for effecting pivoting of the brush sections during the initial portion of each linear stroke of the brush handle. While that pivoting action is taking place, the bristle ends flex but move very little, if at all, across the teeth. It is only after the brush sections reach the pivot stop members that the bristles move across the teeth, and such movement is linear, in the direction of handle movement, not rotational. Therefore, although the brush sections pivot with each change in handle direction, the bristles do not apply the desired rotary brush strokes to the teeth.
There are other prior art toothbrushes wherein longitudinal movement of the brush handle is intended to be converted into some other degree of motion in the brush itself. For example, U.S. Pat. No. 2,660,745 (Yusko) discloses a toothbrush wherein the entire brush head oscillates about the longitudinal axis of the handle in response to longitudinal reciprocation of the handle. The result is an up and down movement of the brush bristles across the surfaces of the teeth. This brushing action was, at one time, considered to be efficient but in recent years has fallen into disfavor among dental professionals.
Still other toothbrushes having bristles that move in relation to the handle or head are found in the following U.S. Pat. Nos.:
______________________________________ U.S. Pat. No. Patentee ______________________________________ 618,690 Ter Laag 1,257,883 Kone 1,911,973 Ruse 2,160,836 Davids 2,184,850 Schloss 2,188,449 Stewart 2,290,454 Steinberg 2,411,610 Aaron 2,799,878 Brausch 2,917,759 Siampaus 3,110,918 Tate, Jr. 3,214,776 Bercovitz 3,994,039 Hadary 4,638,520 Eickmann 4,682,584 Pose 4,766,630 Hegemann ______________________________________
These patents all disclose devices having different brush action than the desirable rotary action described above, but are of general interest in that they show a wide variety of actuating mechanisms for achieving brush movement.